Low voltage neon shorts tester



July 4, 1953 M. PITINSKY I 2,645,754

LOW VOLTAGE NEON SHORTS TESTER Filed Aug. 1, 1952 POWER SUPPLY WJNVENTOR, MORRIS PITINSKY Patented July 14, 1953 OFFICE LOW VOLTAGE NEONSHORTS TESTE Morris Pitlnsky, Eatontown, N. J.

Application August 1, 1952, Serial No. 302,287

(Granted under Title 35, U. S. Code (1952),

sec. 266) 3 Claims.

The invention described herein may be manufactured and used by and forthe Government for governmental purposes, without the payment of anyroyalty thereon.

The present invention relates to a testing device for indicating theexistence of a short circuit between elements of an electron dischargedevice.

In short circuit testing of vacuum tubes it has been customary to employan indicator lamp of the gaseous discharge type in series with asufliciently high minimum potential, generally of the order of 75 to 85volts, and a limiting resistor of sufieient size to prevent damage tothe lamp and to the elements under test. The open circuit voltage, whichmust at least equal the firing voltage of the lamp, is therefore appliedto the elements under test. Because a relatively high voltage is appliedto the elements under test the conventional series type short circuitindicator has not proven entirely satisfactory.

An Object of this invention is to provide an improved short circuitindicating means.

Another object is to provide apparatus arranged to indicate theexistence of a short circuit between elements of an electron dischargedevice which will test for such short circuits without subjecting thatdevice under test to voltages or currents of a magnitude sufficient todamage the device. 1

These and other objects of the invention will become apparent from thedescription and claims that follow.

The invention will be more clearly understood by reference to theattached drawing showing a circuit diagram of a short circuit testingcircuit according to the invention.

In the drawing, a series circuit consisting of a seri s resistor 2, acurrent limiting device such as resisttor 3, and a normally extinguishedindicator lamp, such as a gaseous discharge lamp or neon lamp 4, isconnected between the terminals of a direct or alternating current'powersupply l. Limiting resistor 3 and neon lamp 4' are shunted by resistor5. Each of the two elements of the electron discharge device acrosswhich the short circuit test is to be made isrespectively connected toone or the other of leads 6 and I so that the elements under test areconnected in shunt with series resistor 2. 1

A 75 to 85 volt, alternating or direct current power supply I isgenerally used in operating the equipment. lhe neon lamp 4 is generallychosen to have a 50 to 60 volt alternating or direct current firingpotential. The series resistor 2, limresistor 2 and, subsequently, theelements of the iting resistor 3, and shunt resistor are so chosen thatthe voltage division across the network places approximately 50 voltsacross neon lamp 4 (or slightly less than the firing voltage of neonlamp 4), and approximately volts across load electron discharge devicethat are connected to leads 6 and 1 for short circuit testing. In theevent of a short circuit between the elements under test, resistor 2 isshunted with a relatively low resistance and a larger part of the sourcevoltage is made available across resistor 5 thereby firing andexcitingneon lamp 4 and indicating the presence of the short circuit. When analternating current power source is used it may be desirable to insert acapacitor in the leads 6 or 1 to prevent excitation of lamp 4 due tonormal tube conduction on alternate half cycles.

Limiting resistor 3 were required should be sufiiciently large, about250,000 ohms, for the type of neon lamp discussed herein to preventburning out of the lamp.

Due to the relatively low voltage across the electron discharge deviceelements under test, the test is non-destructive. Also, the circuitherein disclosed is particularly useful for testing miniature type tubesor tubes having closely spaced elements. When the elements under testare spaced close together, and the conventional series short circuitindicator is utilized, a relatively high voltage is placed across theelements and an erroneous short circuit indication may result due to theelectrostatic potential built up across the elements. This problem is,for all practical purposes, eliminated when the low voltage test circuitherein disclosed is utilized.

As many apparentlywidely different embodiments of the invention may bemade without departing from the spirit and scope hereof, it is to.

- terminals, a series resistor, and a normally extinguished indicatorlamp connected in series between said terminals; a resistor connected inshunt across said indicator lamp; and means for charge device or thelike which comprises a plurality of elements: a source of voltage withtwo terminals, a series resistor, a current limiting resistor, and anormally extinguished gaseous discharge lamp connected in series betweensaid terminals; a resistor connected in shunt across said currentlimiting resistor and said indicator lamp; and means for connecting twoselected elements of said device in shunt across said load resistorwhereby said lamp is excited by a short circuit between said twoelements.

3. In an apparatus for testing an electron dis- 77-: charge device orthe like which comprises a plu 7 rality of elements: a source of voltagewith two terminals a series resistor, a current limiting resistor, and anormally extinguished neon lamp connected in series between saidterminals; a resistor connected in shunt across said current limitingresistor and said neon lamp; and means for conneeting twoz selectedelements of said device in shunt across "said series resistor. wherebysaid lamp is excited by a short circuit between said ;10 'two elements.

No references cited.

